Which of the following statements is not true? -1 1/5 < -1.5
1.7>1 1/2
3/4 < 7/8
0.001 < 0.1

Ans: 720

This is equal to the number of different arrangements of three persons from a group of 10 persons 

Required number of ways = 10P3 = 720

OR can be solved in this way
select 3 runners (10C3 ways)
These 3 runners can be arranged in 3! ways
Total = 10C3×3! = 720